In the field of injection molding plastic and/or polymeric material it is known to melt, mix and otherwise process such material by feeding granular material to a screw rotating in a barrel. The screw flights are usually differentially dimensioned to melt the solid plastic and otherwise process and pump the material in liquid form toward an outlet connected to the cavity of a mold. The flights of the screw have various configurations so as to perform a variety of operations and may be more than twenty times the diameter in length. Such a machine is shown in U.S. Pat. No. 3,596,326.
As the material is melted, it is pumped past a non-return valve to a expandable chamber and the screw is forced axially back until a predetermined charge is in the chamber. Rotation of the screw is stopped and the screw is forced toward a nozzle injecting the charge into the mold cavity where the material is cooled or otherwise reacted to solidify in the cavity to form a desired article.
As should be apparent the length of the screw need to perform the desired operations to plasticate and process the material as well as the length of machine needed to accommodate the reciprocation of the screw dictates that such reciprocating screw injection molding machines be of considerable length.
There has been recently developed by the Farrel Division of USM Corporation an apparatus known as the DISKPACK Processor for processing plastic material with greater efficiency than the screw of an extruder or injection molding machine. Such an apparatus is typically shown and described in U.S. Pat. Nos. 4,142,805, 4,329,065 and 4,227,816. These patents show a multi-stage rotary processor for plastic and polymeric materials which are or become in the course of processing viscous liquids. An annular housing rotatably receives a rotor having in its cylindrical surface a plurality of annular channels forming with the close fitting housing a plurality of processing passages. Transfer passages conduct the material from each passage after processing and finally to a relatively narrow and deep channel which provides pumping pressure to force the processed material from an outlet which may be a die for shape extrusion or which may conduct the material for further processing in another device.
In copending application for U.S. Patent Ser. No. 612,682, filed May 22, 1984, there is shown a combination of the plasticating unit known as the DISKPACK Processor and a screw in a sleeve reciprocable in a barrel. The processor acts to melt or otherwise process material to be molded and the screw feeds the processed material to a chamber in the barrel at the end of the screw/sleeve combination. The chamber expands as the screw/sleeve is forced back by the plastic fed into the chamber. When the chamber has received a predetermined charge, the processor and screw are stopped and the unit is moved forward to eject the material from the chamber into the mold cavity. The plasticator comprises a rotor having channels in its cylindrical surface and being rotated in an annular housing. In normal operation, the walls of the channels drag the material toward fixed blocks which restrain the material so as to be processed by shear forces and direct the material from channel to channel and thence to the screw. For certain materials it may be undesirable to stop the rotor during injection due to possible degradation of the material until the rotor again is moved.